I really, really do love the shadow boxes, but the limited wall space and limited storage space in each box makes them less practical for me. Not to mention my girlfriend would truly want to kill me.
I did see a beautiful display case in a furniture store that's got me drooling a bit. Wood-framed glass doors and sides in a case that's a little taller than me and about a yard wide (just short of a meter for the metrically-inclined). But as gorgeous as that is, I don't think it would be as capacious as the bookcase I'm using now. More attractive, perhaps, but not as many cubic inches/meters/cubits/whatevers...